Spectrometry is the art of inferring information about an analyte based on its interaction with electromagnetic fields and radiation. Mass spectrometry (MS), as its name suggests, is concerned with measurements of mass. Mass spectrometers have been called the smallest scales in the world because some of them can ‘weigh’ a single atom. Over time, the use of mass spectrometry has been expanded to larger and larger molecules, including macromolecules. It has also become possible to construct lighter and more compact mass spectrometers, such that some of these instruments are portable, or can even be hand-carried, and can be used in the field; however, these instruments have serious limitations.
Mass spectrometers generally involve a source of ionized analyte, a mass analyzer, and a detector. The mass analyzer and detector operate under reduced pressure relative to the atmosphere, and said reduced pressure can be provided by a vacuum pump. In portable instruments, it can be important to optimize these components to result in a light weight and compact instrument than nonetheless maintains high performance. As mass spectrometry in general has become compatible with larger and larger analytes, MS has been applied frequently in laboratory settings to identify macromolecules or even larger analytes in biological and chemical samples. In the post-genomic era, there is more interest than ever in the characterization of increasingly massive macromolecular assemblies, and even larger bioparticles such as viruses and whole cells. Prior to this invention, the upper bound of the size of analytes suitable for MS with a portable instrument was limited, and the ability to analyze macromolecules without hard vacuum (e.g., <10−5 Torr) was even more limited. Therefore, it was difficult or impossible to perform MS with large analytes outside of a laboratory setting—for example, in forensic, ecological, environmental, anthropological, and archaeological field work, in mobile medical settings such as a van-based clinical or screening enterprise or in developing nations, and in screening for pollutants or contaminants, e.g., for security, food safety, or environmental protection purposes. However, the rewards of such portable technology can include making its analytical power more accessible in a more rapid manner. The reduction in space and cost from a portable instrument can also be useful in laboratory applications, including biomedical research in fields such as proteomics, genomics, metabolomics, and biomarker discovery, and in structural studies and characterization of nanomaterials.